Chapter 3 Sensing & Responding Human Performance Engineering Robert W. Bailey, Ph.D. Third Edition

Responders Sensors Figure 4-1 Simplified model of human information processing with the sensors emphasized

 Sensing is done by specialized nerves called receptors.  Ex. Pain receptors- spread throughout the body Ex. Eyes- Concentrated in one location

Senses: Vision, Hearing, Smell, Taste, Touch Cold, warmth, pain, kinesthetic (movement), vestibular (movement through space)

Sensing VS. Perception Sensing is the capture and transformation of information required for the process of perception to take place. Perception can be enhanced with experience.

Threshold - The point on an intensity scale below which we do not detect the stimulus and above which we do. Difference threshold - The minimum physical difference that produces a perceptible difference.

Table 4.1 Various Forms of energy and the senses each stimulates StimuliSense ElectromagneticVision MechanicalHearing Touch Pain Vestibular Kinesthetic ThermalCold Warm ChemicalTaste Smell (Adapted from Human Behavior: A System Approach. By N. W. Heimstra and V.S. Elingstad. Copyright ©1972 by Wadsworth Publishing Company, Inc. Reprinted by permission of the publisher. Brooks/Cole Publishing Company. Monterey, California.)

Table 4.2 Some Approximate Sensory Thresholds SenseDetection Threshold SightCandle flame seen at 30 miles on a dark clear night HearingTick of a watch under quiet conditions at 20 feet TasteTeaspoon of sugar in 2 gallons of water SmellDrop of perfume diffused into the entire volume of a three-room apartment Touch Wing of a bee falling on your cheek from a distance of 1 centimeter (Adapted from Galanter, 1962)

What is the most important sense?

Vision The light that stimulates the eye is a form of electromagnetic radiation. The eye converts the light into a form that can be used by the brain.

The Sensity of the eye depends on: Size of stimulus, brightness and contrast of the stimulus, size of visual field, region of retina stimulated

Common Visual Defects:  Hyperopic- Eyeball is shorter than normal  Myopic- Abnormally long eye ball  Night Blindness – Vitamin A deficiency

We will discuss only three of several visual deficiencies that could exist and that are correctable if recognized. Two of the most common correctable visual defects, hyperopic and myopia (nearsightedness), are usually due to shape abnormalities in the eyeballs. Figure 4-8 illustrates the structure of normal, hyperopic, and myopic eyes. Normal: Light Focuses on the retina Hyperopia: Light focuses in back of the retina for near objects Myopia: Light focuses in front of the retina for far objects

What are two visual deficiencies not correctable? Blindness & Color Blindness (Red, Green, Gray) 8% of Men, 1% of Women

Hearing 19% of working-age Americans have a hearing impairment Frequency – pitch, intensity – loudness

Sound Pressure Level (d8) Threshold of hearing Whisper Quiet Office, Household sounds Normal conversation Average auto; loud radio 90 Truck or bus Subway train Loud Thunder Painful sound Ear damage possible Figure 4-10 Sound pressure levels for typical sounds

What are cutaneous senses?

Related to the Surface of the Body: Touch (Pressure)-experienced when a depression is formed on the skin. Pain- can motivate and deteriorate human performance more than any other stimulus. Temperature – Cold & Warmth Skin Temperature – 91.4 F

Taste- Sweet, Sour, Salty, & Bitter Smell- 6 Qualities: Spicy, Fruity, Burnt, Resinous, Flowery, & Putrid 10,000 times as sensitive as taste Kinesthetic (muscle sense) 3 rd most important sense related to human performance. It provides information on: The position of the limbs, How far they have moved, The posture of the body as a whole.

Vestibular- Provides people with information about their position in a three – dimensional space and their movement through space. Located in the inner ear. * Sensory adaptation & sensory interaction